KR20240142549A - Improvement of etching uniformity in radical etching using a sealing ring - Google Patents

Abstract

A sealing ring for use in a process chamber includes a tube extension configured to surround a process zone within the process chamber. An upper end of the tube extension is configured to be connected to a showerhead of the process chamber and a lower end is configured to extend into the process zone and proximate an edge ring surrounding a wafer received within the process zone. A foot extension has an inner end coupled to the lower end of the tube extension and extending outwardly from the process zone to the outer end. The foot extension provides an annular surface configured to form a gap with an uppermost surface of the edge ring.

Description

Improved etching uniformity in radical etching using a sealing ring

The present invention relates to components usable in a semiconductor process chamber for controlling radicals, and more particularly, to a sealing ring for improving etching rate non-uniformity on the surface of a wafer.

Semiconductor wafers are exposed to various manufacturing processes to create electronic devices. The processes used to create electronic devices include, among others, deposition processes, etching processes, and patterning processes. The etching process is performed in a process chamber (also referred to as an 'etcher'). In radical etching, relatively low energy ions or radicals are generated in a plasma and directed onto the surface of a substrate that is received on a grounded electrode. Excess radicals and process gas(es) are then removed from the etcher through an exhaust port.

In a specific radical etch chamber, tests were performed and specific non-uniformities in the etch were measured. The data collected from the testing and experiments indicate that the etch rate tends to decrease progressively from the center of the wafer toward the wafer edge, and then increases significantly near the wafer edge. Since the cost of manufacturing semiconductor devices is significant, chip designers generally want to increase the semiconductor device density all the way to the wafer edge. Since semiconductor devices manufactured near the wafer edge exhibit etch-induced device performance degradation, etch non-uniformities near the wafer edge can result in yield loss near the wafer edge.

In this context, an embodiment of the present invention arises.

Various implementations of the present disclosure include devices and systems used to confine plasma radicals within a process zone of a process chamber. During an etching process (e.g., dry etching), plasma is generated within the process chamber by ionizing process gas(es) via a high frequency electromagnetic field. In the process chamber, the generated plasma is directed over a surface of the wafer. The plasma may be generated locally within a process zone defined within the process chamber or remotely outside the process zone. The generated plasma comprises ions, electrons, and radicals. When the plasma is generated remotely, radicals from the plasma are supplied to the process zone via a showerhead or nozzle or other delivery mechanism.

In one embodiment, a sealing ring is used in the process chamber to substantially seal plasma radicals over the surface of the wafer. The sealing ring includes a foot extension positioned over the edge ring along a periphery of the wafer, for example, approximately surrounding an edge of the wafer. The separation between the foot extension and the edge ring can be configured to control exhaust flow of radicals and process gas(es) out of the process zone. As described in more detail below, this flow control is used to influence the velocity of the radicals near the edge of the wafer to improve etch rate uniformity near the wafer edge.

In one embodiment, the sealing ring is coupled to the bottom surface of the showerhead. The sealing ring includes a tube extension extending downwardly from the showerhead and surrounding the process region. The foot extension can be integrally formed with a lower end of the tube extension. In one configuration, the tube extension forms a wall surrounding the process region. In some implementations, the tube extension can be aligned with an edge of a wafer received within the process chamber. In some implementations, the tube extension can extend perpendicular to the bottom surface of the showerhead. In some implementations, the tube extension can be angled inwardly or outwardly from an axis perpendicular to the bottom surface of the showerhead. In some implementations, the foot extension is generally horizontal and parallel to the surface of the wafer received within the process chamber. In some implementations, the foot extension can be angled such that it is not parallel to the surface of the wafer received within the process chamber. The foot extension can have a width similar to the width of the edge ring surrounding the wafer support surface.

The etch rate non-uniformity observed at the wafer edge may be caused by back diffusion of reaction byproducts from the edge ring to the edge of the wafer. Back diffusion leads to an increased concentration of unwanted plasma radicals at the wafer edge. The sealing ring disclosed herein is designed to reduce back diffusion and, along with it, the concentration of unwanted plasma radicals at the wafer edge. Additionally, the increased concentration of plasma radicals at the wafer edge may be due to the edge ring material. Typically, the edge ring is made of a material (e.g., aluminum oxide) that does not consume fluorine in plasma radicals as much as the surface of the wafer adjacent the edge ring. This lack of fluorine consumption by the edge ring due to the difference in materials may contribute to the build-up (i.e., increased concentration) of fluorine-containing plasma radicals at the wafer edge.

In one embodiment, a sealing ring for use in a process chamber is disclosed. The sealing ring includes a tube extension and a foot extension. The tube extension is configured to surround a defined process zone within the process chamber and extends between its upper end and its lower end. The upper end is connected to a showerhead of the process chamber. The tube extension extends downwardly from the upper end such that the lower end approximates an edge ring surrounding a wafer receiving surface. The foot extension extends between its inner end and its outer end, the outer end of which defines an outer diameter of the sealing ring. The inner end engages the lower end of the tube extension, and the outer end extends outwardly from the process zone. The foot extension provides a sealing annular surface that forms a gap with an uppermost surface of the edge ring.

Other aspects and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings, which illustrate by way of example the principles of the present invention.

FIG. 1A illustrates a cross-sectional side view of a process chamber used to perform an etching operation using radical etching, the process chamber utilizing a sealing ring and, in one embodiment, shown in an active state (i.e., process ready state).
FIG. 1b illustrates a cross-sectional side view of the process chamber of FIG. 1a with the process chamber depicted in an inactive state.
FIG. 1c illustrates a cross-sectional side view of the process chamber of FIG. 1a with the process chamber shown in an active state for use in performing a waferless auto clean (WAC) operation, in one embodiment.
FIG. 2a illustrates a vertical cross-section of a portion of a showerhead having a sealing ring coupled thereon, in one embodiment.
Figure 2b illustrates a profile of the sealing ring illustrated in Figure 2a in an alternative embodiment.
Figure 2c illustrates a profile of the sealing ring illustrated in Figure 2a in yet another alternative embodiment.
FIG. 2d illustrates a profile of the sealing ring illustrated in FIG. 2a in yet another alternative embodiment.
FIG. 2e illustrates a profile of the sealing ring illustrated in FIG. 2a in yet another alternative embodiment.
FIG. 2f illustrates a profile of the sealing ring illustrated in FIG. 2a in another alternative embodiment.
FIG. 2g illustrates a profile of the sealing ring illustrated in FIG. 2a in yet another alternative embodiment.
FIG. 3 is a graph detailing the etch rate from the center of the wafer to the edge of the wafer when a sealing ring having a foot extension is used to seal plasma in a process region of a process chamber as a function of different gap distances, in one embodiment.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent to one skilled in the art that the present invention may be practiced without some or all of these specific details. In other instances, well-known process operations have not been described in detail so as not to unnecessarily obscure the present invention.

The present disclosure provides various details of a sealing ring and system that uses the sealing ring to process a semiconductor substrate (i.e., a wafer). It should be appreciated that the present disclosure may be implemented in a number of ways, such as a process, an apparatus, a system, a device, or a method. Some examples of implementations are described below.

A sealing ring used in a process chamber to confine radicals within a process zone is disclosed herein. The sealing ring is designed to control the flow and exhaust of radicals and other gas(es) out of the process zone during an etching operation. In one embodiment, the sealing ring employed in the process chamber is used to reduce the radical concentration across an edge region of the wafer. In one example, the sealing ring is coupled to a bottom surface of a showerhead disposed in an upper portion of the process chamber. In one configuration, the showerhead discussed herein is used to induce collisions of ions with the showerhead hardware, thereby neutralizing them but allowing the radicals to flow into the process zone.

In some implementations, the sealing ring includes a tube extension and a foot extension. The tube extension has a length and extends downward from the showerhead and surrounds a portion of the process zone within the process chamber. The foot extension can be integrally connected to a lower end of the tube extension and extends outwardly away from the process zone. The foot extension forms an annular surface that allows for control of the separation between the foot extension and the edge ring. In operation, the separation between the foot extension and the edge ring allows for control of the rate at which radicals and other gas(es) flow out of the process zone. This control allows for reduced back diffusion of byproducts resulting from etching on the surface of the edge ring, thereby reducing the concentration gradient of radicals at the wafer edge and correspondingly increasing the etch rate uniformity at the wafer edge (e.g., the outer 20 mm of a 300 mm wafer).

In some implementations, the foot extension of the sealing ring is designed to create a narrow gap between the edge ring and the foot extension. The gap provides a path for radicals to exit the process zone and flow toward an exhaust port provided in the lower portion of the process chamber. In some implementations, the gap is sufficiently narrow so that radicals exiting the process zone have an increased velocity as they flow toward the exhaust port. The rate of radical removal from the process zone affects the concentration gradient of radicals across the wafer edge. By increasing the rate of radical emission, the concentration of unwanted radicals near the wafer edge is reduced, thereby achieving better etch rate uniformity at the wafer edge. Thus, by varying the dimensions and/or shape of the foot extension of the sealing ring, the profile of the gap between the edge ring and the foot extension can be adjusted, and the radical emission rate and ultimately the etch rate can be controlled to increase etch rate uniformity across the entire wafer.

The various features of the sealing ring will now be discussed with reference to the drawings.

FIG. 1A is a simplified diagram of a process chamber (100) used to process a wafer (W), according to some implementations of the present invention. In some implementations, the process chamber (100) is a single-station chamber in that a single wafer is processed at any given time. The process chamber (100) includes an upper portion (102) that accommodates an inner chamber (103) and a lower portion (104) that accommodates a pedestal (105). The inner chamber (103) includes a plasma dome (103a). An aperture (103b) is defined at an upper portion of the plasma dome (103a). The aperture (103b) is used to supply process gas(es) from one or more gas sources (110) for generating plasma. The upper portion (102) of the process chamber (100) includes a showerhead (106). A showerhead (106) is used to flow process gas(es) and radicals into the process zone (122) and to neutralize the ions through collisions within the showerhead (106) before the ions enter the process zone (122). Ion collisions typically occur in the top showerhead (106a) and the bottom showerhead (106b) when the top showerhead (106a) and the bottom showerhead (106b) are arranged in a non-line-of-sight (i.e., non-linear) orientation with respect to one another. The flow of process gas(es) supplied to the inner chamber (103) can be adjusted using one or more flow valves (112) coupled to gas source(s) (110).

In one embodiment, a first end of the coil (108) is coupled to a power source, such as a radio frequency (RF) power source (e.g., a first RF power source) (114), and a second end of the coil (108) is connected to ground. The coil (108) provides RF power to process gas(es) contained in a plasma dome (103a) of the inner chamber (103) to generate a plasma. As illustrated, a matching network (116) is provided to efficiently couple RF power from the RF power source (114) to the coil (108). The RF power source (114) is coupled to a controller (118) that is used to control the RF power supplied to the coil (108).

An inlet is provided to the top showerhead (106a) to supply radicals and ions from the plasma generated in the plasma dome (103a) to the bottom showerhead (106b). In some implementations, the top showerhead (106a) is connected to the bottom showerhead (106b) using, for example, fasteners, connectors, screws, O-rings, or the like. In other implementations, the top and bottom showerheads (106a, 106b) are fabricated from a single piece of metal. The lower portion (104) of the process chamber (100) includes a pedestal (105). In some implementations, the pedestal is an electrostatic chuck (ESC). The top surface of the ESC pedestal (or simply referred to as “ESC”) (105) includes a wafer receiving surface (not shown). A wafer is received on the wafer receiving surface for processing. An edge ring (126) is positioned adjacent to and surrounds the wafer received on the wafer receiving surface. The ESC (105) is coupled to a power source, such as a second RF power source (117), via a corresponding matching network (i.e., a second matching network) (115). The ESC (105) is coupled to a pedestal height adjuster (120) to allow the ESC (105) to move vertically up or down. The pedestal height adjuster (120) is in turn coupled to a controller (118). The pedestal height adjuster (120) uses signals from the controller (118) to adjust the height of the ESC (105). A sealing ring (130) is disposed below the bottom showerhead (106b) and is used to surround a process zone (122) defined in the process chamber (100).

In one embodiment, the pedestal height adjuster (120) can change the height of the ESC (105) such that the ESC (105) is closer or farther away from the bottom surface of the foot extension (134) of the sealing ring (130). Accordingly, this height adjustment enables adjusting the gap (i.e., separation distance) between the bottom surface of the foot extension (134) and the top surface of the edge ring (126) positioned on the top surface of the ESC (105). For example, in FIG. 1A, the ESC (105) is at a height (h1), which positions the separation between the bottom surface of the foot extension (134) and the top surface of the edge ring (126) at a height (or separation distance) (h2). This position may be referred to as an operational position at which etching is performed. Thus, the foot extension (134) of the sealing ring (130) allows for modification of the rate at which radicals and other gas(es) are removed from the process zone (122). For example, when the separation (h2) is further reduced but greater than zero, the rate at which radicals are removed from the process zone (122) increases near the wafer edge. The rate at which radicals are removed from the process zone (122) can be adjusted by varying the separation (h2) distance to be greater than zero. In general, the smaller the separation (h2), the faster the emission rate, and thus the lower the concentration of unwanted radicals near the wafer edge. In this implementation, the sealing ring (130) can be hard-mounted to the upper portion of the process chamber. In other implementations, the sealing ring (130) can be mounted to the upper portion of the process chamber using fasteners, connectors, screws, O-rings, or the like. In yet other implementations, the sealing ring (130) can be mounted to the upper portion of the process chamber using an adjustable mount. For example, the sealing ring (130) is mounted on the bottom showerhead (106b) or on a structure immediately adjacent to the showerhead (106). In some implementations, the structure immediately adjacent to the showerhead (106) may be a top plate (not shown).

In some implementations, the separation (h2) between the bottom surface of the foot extension (134) and the top surface of the edge ring (126) can be controlled by lowering or raising the sealing ring (130). The sealing ring (130), mounted on or next to the showerhead (106), is coupled to a motor (not shown), which in turn is coupled to a controller (118). Signals from the controller (118) are used to adjust the position of the sealing ring (130), which leads to separation. In various implementations, only the sealing ring (130) adjustably mounted on the upper portion of the process chamber is moved to adjust the separation, or only the showerhead (106) with the sealing ring (130) mounted is moved to adjust the separation, or only the ESC (105) is moved to adjust the separation, or both the sealing ring (130) adjustably mounted on the upper portion of the process chamber and the ESC (105) are moved to adjust the separation, or both the showerhead (106) with the sealing ring (130) mounted and the ESC (105) are moved to adjust the separation. The movement of the showerhead (106) with the sealing ring (130) mounted and the ESC (105) can be controlled independently or jointly using signals from the controller (118).

Because of the difference in material seen at the wafer-to-edge ring interface by the radicals, the concentration of radicals is believed to increase near the wafer edge. Typically, the wafer is fabricated from silicon and may include polysilicon material. In contrast, if the edge ring is fabricated from a material such as alumina (i.e., aluminum oxide), which does not consume fluorine during etching, more fluorine tends to diffuse backwards toward the wafer edge and is available for secondary reactions around the edge of the wafer. As a result, a substantial increase in backward diffusion of radicals is observed to occur at the wafer edge, which leads to non-uniformities in the etch. Advantageously, the sealing ring (130) of the present disclosure can be configured to prevent backward diffusion of radicals by increasing the rate of radical emission from the process zone (122) near the wafer edge. As illustrated in FIG. 1a, an exemplary flow line illustrates how radicals have an increased velocity as they exit the process zone (122) through a gap (136) of height (h2) formed between the foot extension (134) and the edge ring (126).

Still referring to FIG. 1a, as described above, the sealing ring (130) includes a tube extension (132) coupled to the bottom showerhead (106b) and forming a sidewall surrounding the process zone (122). A foot extension (134) defines an annular surface extending outwardly from the bottom of the tube extension (132) and away from the process zone (122). The sealing ring (130) is fabricated from a conductive material, such as, for example, aluminum. In some examples, the sealing ring (130) is fabricated from aluminum that is coated with a dielectric material. In some implementations where the ESC (105) is coupled to a second RF power source (117) via a second matching network (115), the sealing ring (130) may be fabricated from a ceramic or other insulating material to avoid RF coupling to the sealing ring (130). As illustrated, the tube extension (132) of the sealing ring (130) extends downward to a height (H1). As noted above, the ESC (105) may be moved to a position suitable for the etching operation. Additionally, in this example, the bottom surface of the bottom showerhead (106b) is at a height (H2) from the top surface of the wafer. In this example, the height (H2) is equal to the height (H1 + h2) (i.e., the height of the tube extension (132) of the sealing ring (130) + the height of the gap (136) between the annular surface (i.e., the bottom surface) of the foot extension (134) and the top surface of the edge ring (126). The gap (136) provides a passage (i.e., a path) through which radicals and gas(es) are pressurized from the process zone (122) toward the exhaust port (128) defined in the lower portion (104) of the process chamber (100).

As mentioned, narrowing the passageway results in an increase in the emission rate of radicals exiting the process zone (122). The increase in velocity may be due to the process chamber (100) attempting to maintain a balance within the process zone (122) between the inflow and outflow of radicals and gas(es). The increase in outflow velocity results in inhibition of backward diffusion of radicals and a decrease in the concentration gradient of radicals at the wafer edge.

FIG. 1b illustrates a simplified diagram of the process chamber (100) with the ESC (105) in a lowered position. In the lowered position, a wafer can be transferred to or removed from the process chamber (100). As described above, the pedestal height adjuster (120) can control the up or down movement of the ESC (105), in which case the ESC (105) is moved downward to a height (h3). This position increases the gap (136) between the foot extension (134) and the edge ring (126) to a height (h4) (i.e., h4 > h2). In some cases, the ESC (105) can be lowered to a position between the operating position (illustrated in FIG. 1a) and the lowered position (illustrated in FIG. 1b) to perform an etching operation or other operation.

FIG. 1C illustrates a cross-sectional view of a process chamber (100) in which a Waferless Auto Clean (WAC) operation is performed. In the WAC operation, radicals and ions are used to clean the internal surfaces surrounding the process zone (122) of the process chamber (100). The internal surfaces surrounding the process zone (122) may exhibit an accumulation of polymers and other byproducts released during the etching operation. Consequently, the WAC operation is performed periodically between sessions of wafer etching. As illustrated, the ESC (105) is also coupled to an RF power source (117) via a corresponding matching network (115).

In some implementations, the sealing ring (130) is fabricated from a conductive material. In such implementations, the sealing ring (130) is connected to ground to provide an RF return path to ground for RF current from the ESC (105) powered from the process zone (122). In some implementations, a ground disconnect (140) is provided. The ground disconnect (140) is configured to disconnect the structure of the sealing ring (130) from ground, allowing the sealing ring to electrically float.

The ground disconnect (140) may be a switch or mechanical element that can be moved to connect or disconnect an electrical connection. In some implementations, the ground disconnect (140) is an RF switch. When the RF connection is disconnected, the mechanical sealing ring (130) may still be connected to the showerhead (106) using a type of insulator connector. In one example, the controller (118) may set the ground disconnect (140) to be RF floated or RF connected. In one embodiment, the ground disconnect (140) may have a motor that enables mechanical movement of the switch or connector.

By RF floating the sealing ring (130), the RF power will find an alternate path to ground. The alternate path may be, for example, through the showerhead (106) or the interior wall of the process chamber (100). RF floating the sealing ring (130) is not limited to WAC operations. Rather, the sealing ring (130) may be RF floated during other etching operations that require RF power from the ESC (105) to power the plasma in the process zone (122).

FIG. 2a illustrates an enlarged cross-sectional view of a sealing ring (130) used in a process chamber (100), according to some implementations. The sealing ring (130) is configured to seal radicals and gas(es) within the process zone (122) and control the removal of radicals from the process zone (122). The sealing ring (130) may be coupled to the bottom showerhead (106b) using a fastener, connector, screw, or the like. Additionally, an optional O-ring (139) may provide a seal between the sealing ring (130) and the bottom showerhead (106b). For example, the top surface of the sealing ring (130) includes a groove (138) into which the O-ring (139) is received. The sealing ring (130) is coupled to the bottom showerhead (106b) by compressing the O-ring to seal the gap. In other embodiments, the seal ring (130) may be coupled to a structure external to the radius of the showerhead (106), or may extend externally. Although not explicitly shown in the drawings, in some embodiments, more than one O-ring, and/or different types of seals, may be used independently, or in conjunction with one or more O-rings, to seal any gap between the seal ring (130) and the bottom showerhead (106b).

As previously mentioned, the sealing ring (130) includes a tube extension (132) and a foot extension (134). The tube extension (132) extends downwardly between its upper end and its lower end. The foot extension (134) extends between its inner end (facing toward the process zone) and its outer end (facing away from the process zone). The lower end of the tube extension (132) is connected to or otherwise integral with the inner end of the foot extension (134). In this example, the tube extension (132) extends perpendicularly (SA) between its upper end and its lower end and is perpendicular to the bottom surface (107) of the bottom showerhead (106b). The tube extension (132) extends a height (H1) such that its lower end proximates the edge ring (126) (which is received on the ESC (105)). In some implementations, the term 'proximate' is defined as a separation distance between the top surface of the edge ring (126) of the sealing ring (130) and the bottom surface of the foot extension (134) being from 1 mm to 50 mm. In some implementations, the separation distance can vary by +/- 20% of the aforementioned range. In some implementations, the separation distance between the top surface of the edge ring (126) of the sealing ring (130) and the bottom surface of the foot extension (134) is defined as about 37 mm. In alternative implementations, the separation distance between the top surface of the edge ring (126) of the sealing ring (130) and the bottom surface of the foot extension (134) is defined as about 50 mm. Examples of tested separation distances are discussed with reference to FIG. 3. As discussed above, this is an adjustable parameter that can be set depending on the process being performed, the gas(es) being used, and other operating parameters. Thus, the foot extension (134) between the inner end and the outer end defines an annular surface. The term 'about' is defined to include a deviation of +/- 15% of the specified value.

In some implementations, the tube extension (132) is configured to be aligned over an outer edge of a wafer receiving surface defined on the ESC (105). The tube extension (132) provides a sidewall surrounding the process zone (122) such that radicals and gas(es) can be substantially sealed over the wafer during operation. In some implementations, the width of the annular surface of the foot extension (134) is defined to at least partially cover the width of the surface of the edge ring (126). In some implementations, the width of the annular surface of the foot extension (134) substantially covers the entire width (W1) of the surface of the edge ring (126). In some implementations, the width (W2) of the foot extension (134) is longer than the W1 of the edge ring (126) such that when the tube extension (132) is aligned with the outer edge of a wafer (W) received on the ESC (105), the outer edge of the foot extension (134) will extend beyond the width (W1) of the edge ring (126) received adjacent the outer edge of the wafer (W). In some implementations, the width (W2) of the foot extension (134) is longer than the width (W1) of the edge ring (126) such that when the outer edge of the foot extension (134) is aligned with the outer edge of the edge ring (126) received adjacent the wafer (W), the inner edge of the foot extension (134) may align with or overlap an area above the edge of the wafer.

The foot extension (134) is, in some implementations, defined to be orthogonal to the tube extension (132), with the annular surface of the foot extension (134) being substantially parallel (+/- 5%) to the edge ring (126). Still referring to FIG. 2A, the gap (136) defined between the annular surface of the foot extension (134) and the edge ring (126) is substantially uniform over the length of the gap (136) (i.e., the height (h2) of the gap (136) along the annular width of the foot extension (134) is uniform). The passage defined by the gap (136) can be configured to cause an increase in the emission rate of radicals and gas(es) emanating from the process zone (122) from V1 to V2 (i.e., V2 > V1). The height (h2) of the gap (136) should also be set so that the gap is not too narrow that it creates a bottleneck. For example, a gap (136) of less than about 1 mm could potentially lead to increased backward diffusion of radicals into the process zone (122).

FIGS. 2b-2g illustrate non-limiting examples of different profiles of a sealing ring (130) that may be used in a process chamber (100) to seal the radicals and shape the exhaust flow beneath the foot extension (134). FIGS. 2b, 2c, 2f, and 2g illustrate different profiles of the tube extension (132), and FIGS. 2d, 2e, and 2f illustrate different profiles of the foot extension (134). Referring to FIG. 2b, the tube extension (132) is positioned at an angle (α°) with respect to the right angle (SA). The tube extension (132) extends downwardly and inwardly toward the process zone (122). The angle (α°) created by the angled tube extension in FIG. 2b is different from the vertical angle with respect to the bottom showerhead (106b) illustrated in FIG. 2a.

As in the implementation of FIG. 2a, the tube extension (132) of the sealing ring (130) illustrated in FIG. 2b extends to a height (H1) between the upper end and the lower end. The foot extension (134) is coupled to the lower end of the tube extension (132) so as to be substantially parallel (+/- 5%) to the edge ring (126) and the bottom showerhead (106b). The lower end of the tube extension (132) is aligned around the outer edge of the wafer. Additionally, in this implementation, the outer end of the foot extension (134) is aligned with the outer edge of the edge ring (126). An annular surface of the foot extension (134) defined between the inner end and the outer end extends to a width (W2). The width (W2) of the annular surface of the foot extension (134) is greater than the width (W1) of the edge ring (126). A gap (136) defined between the annular surface of the foot extension (134) and the edge ring (126) is substantially uniform (+/- 5%) and extends to a height (h2). The emission rate of radicals flowing from the process zone (122) increases from V1 to V2 as they flow through the passage of the gap (136) (i.e., V2 > V1). Again, the increasing rate (V2) can be adjusted by setting the gap (136) to a separation that is most effective in reducing the non-uniformity of the etch rate at the wafer edge.

FIG. 2c illustrates an alternative sealing ring profile to that illustrated in FIGS. 2a and 2b in one implementation. In this implementation, the tube extension (132) is positioned at an angle (β°) with respect to the right angle. Additionally, the tube extension (132) extends downwardly and outwardly away from the process zone (122). The tube extension (132) of the sealing ring (130) extends a height (H1) between its upper end and its lower end. The foot extension (134) extends from the lower end of the tube extension (132) and is substantially parallel to the edge ring (126) and the bottom showerhead (106b).

FIG. 2d illustrates another sealing ring profile for one implementation, relative to those illustrated in FIGS. 2a through 2c. In FIG. 2d, the tube extension (132) extends vertically downward from its upper end to its lower end, perpendicular to the bottom showerhead (106b). However, the foot extension (134) extends downward at a different angle from the vertical with respect to the tube extension (132).

In FIG. 2d, the foot extension (134) extends downward from the inner end of the sealing ring (130) to the outer end at a taper angle (θ°) with respect to the vertical. The tube extension (132) is aligned with the inner edge of the edge ring (126), and the outer end of the foot extension (134) is aligned with the outer edge of the edge ring (126). The height of the tube extension (132) of the sealing ring (130) between the upper end and the lower end is H1, and the width of the annular surface of the foot extension (134) is equal to the width (W1) of the edge ring (126). In some implementations, the outer end of the foot extension (134) may extend a width that is longer or shorter than the outer edge of the edge ring (126). Due to the downward slope of the foot extension (134) from the tube extension (132), the height of the gap (136) between the annular surface of the foot extension (134) and the edge ring (126) is not uniform (i.e., can vary) across the width of the foot extension (134). Instead, the height of the gap (136) gradually decreases from a height (h2) at the inner end of the foot extension (134) to a height (h5) at the outer end of the foot extension (134), where h2 > h5. Due to the additional narrowing of the gap (136) at the outer end of the foot extension (134), the radicals and other gas(es) flowing through the gap (136) are accelerated toward the exhaust port (128), causing the emission velocity to increase from V1 (i.e., the velocity measured before the radicals enter the gap (136)) to V2' (i.e., the velocity measured when the radicals exit the gap (136)) (i.e., V2' > V1). For example, the emission velocity (V2') may be greater than the emission velocity (V2) of FIGS. 2a-2c. Although not explicitly shown in the drawings, in some embodiments, the top surface or edge ring (126) may be tapered to a thickness of the inner diameter that is greater than the thickness of the outer diameter. In such embodiments, the difference between h2 and h5 will be smaller compared to that illustrated in FIG. 2d. In some such cases, h2 will be substantially equal to h5.

FIG. 2e illustrates another sealing ring profile for those illustrated in FIGS. 2a-2d. As in FIG. 2d, the tube extension (132), in this implementation, extends vertically downward from the upper end to the lower end and is substantially perpendicular (+/- 5%) to the bottom showerhead (106b). The foot extension (134) tapers upward from the inner end to the outer end at a taper angle (γ°) with respect to the vertical. The inner ends of the tube extension (132) and the foot extension (134) are aligned with the inner edge of the edge ring (126), and the outer end of the foot extension (134) is aligned with the outer edge of the edge ring (126). The height of the tube extension (132) of the sealing ring (130) between the upper end and the lower end is H1, and the width of the annular surface of the foot extension (134) is equal to the width (W1) of the edge ring (126). Due to the upward and outward slope of the foot extension (134) toward the outer end, the height of the gap (136) between the annular surface of the foot extension (134) and the edge ring (126) is not uniform across the width of the foot extension (134). Instead, the height of the gap (136) gradually increases from a height (h2) at the inner end of the foot extension (134) to a height (h6) at the outer end of the foot extension (134), where h6 > h2.

The edge ring (126) is positioned so that the top surface of the edge ring (126) is flush with the top surface of the wafer (W). A passage defined by a gap (136) that increases in height from an inner end to an outer end of the foot extension (134) is set to cause an increase in the emission rate of radicals and gas(es) emanating from the process zone (122) from V1 (i.e., the velocity of the radicals before they enter the gap (136)) to V2" (i.e., the velocity measured as the radicals pass through the narrow inner end of the gap (136)) (i.e., V2" > V1). However, the emission rate decreases from V2" at the inner end of the gap (136) to V2"' at the outer end. The decrease in the emission rate may be due to the increasing height of the gap (136) toward the outer end. The emission rate (V2'') is still greater than the emission rate (V1) in the process zone (122), but is less than the emission rate (V2) of FIGS. 2a-2c and V2' of FIG. 2d.

FIG. 2f illustrates an alternative implementation, another sealing ring profile for those illustrated in FIGS. 2a-2e. In this implementation, the tube extension (132) extends from the upper end to the lower end at an angle (β°) that is different from the vertical (+/- 5%) with respect to the bottom surface (107) of the bottom showerhead (106b). The outward slope angle of the tube extension (132) is illustrated as similar to that illustrated in FIG. 2c. In some implementations, the outward slope angle of the tube extension (132) can be greater than or less than β°. In addition to the outward slope of the tube extension (132), the foot extension (134) is also illustrated as tapering downward from the inner end to the outer end at a taper angle (θ°). The downward slope angle of the foot extension (134) is illustrated as similar to that illustrated in FIG. 2d.

In an alternative implementation, the downward slope angle of the foot extension (134) can be greater than or less than θ° with respect to the vertical. The tube extension (132) is aligned at its upper end with the inner edge of the edge ring (126), and the outer end of the foot extension (134) is aligned with the outer edge of the edge ring (126). The height of the tube extension (132) of the sealing ring (130) between the upper end and the lower end is H1, and the width of the annular surface of the foot extension (134) is equal to the width (W1) of the edge ring (126). Due to the downward slope of the foot extension (134) outward from the tube extension (132), the height of the gap (136) between the annular surface of the foot extension (134) and the edge ring (126) is not uniform across the width of the foot extension (134). Instead, the gap height gradually decreases from a height (h2) at the inner end of the foot extension (134) to a height (h5) at the outer end of the foot extension (134), where h2 > h5. The edge ring (126) is positioned so that the top surface of the edge ring (126) is flush with the top surface of the wafer (W). Due to the additional narrowing of the gap (136) from the inner end to the outer end of the foot extension (134), the radicals flowing through the gap (136) are accelerated as they pass through the initially narrowed end of the gap (136) toward the exhaust port (128), resulting in an increase in their exit velocity from V1 (i.e., the velocity measured before the radicals enter the gap (136)) to V2' (i.e., the velocity measured when the radicals exit the gap (136), where V2' > V1. Although not explicitly shown in the drawing, in some embodiments, the top surface or edge ring (126) may be tapered to a thickness of the inner diameter that is greater than the thickness of the outer diameter. In such embodiments, the difference between h2 and h5 in FIG. 2f will be smaller. In some such cases, h2 will be substantially equal to h5.

FIG. 2g illustrates another alternative sealing ring profile in one implementation. In this implementation, the sealing ring (130) includes a plurality of segments. For example, the sealing ring (130) includes a tube extension (132), a first segment (132a), a second segment (132b), a third segment (132c), and a foot extension (134). The tube extension (132) of the sealing ring (130) extends vertically downward from its upper end to its lower end. The first segment (132a) extends along a horizontal axis from its upper end and is used to couple the sealing ring (130) to the bottom showerhead (106b). The first segment (132a) extends away from and outwardly from the process zone (122). The second segment (132b) extends downward orthogonal to the first segment (132a) from its upper end to a height (H3). The third segment (132c) extends downwardly from the bottom of the second segment (132b) to an outer end of the foot extension (134) at a height (H4). In some implementations, the third segment (132c) extends downwardly and inwardly at an angle (δ°) relative to a right angle. The foot extension (134) extends a width (W1) between the inner end and the outer end.

In some implementations, the sealing ring (130) has a different design (not shown) than that illustrated in FIG. 2g. In such implementations, the plurality of segments of the sealing ring (130) include a first segment (132a), a second segment (132b), a third segment (132c), and a foot extension (134), wherein the first, second, and third segments (132a, 132b, 132c) together define a tube extension (132). The positions and orientations of the first, second, and third segments (132a, 132b, 132c) and the foot extension (134) are similar to those illustrated in FIG. 2g. In this implementation, the design of the sealing ring (130) differs from the design of the sealing ring (130) illustrated in FIG. 2g in that the sealing ring (130) of FIG. 2g includes an additional tube extension (132) that extends vertically downward from the bottom surface (107) of the bottom showerhead (106b).

Various sealing ring profiles are provided as mere examples and other profiles may also be envisioned, such as a tube extension (132) comprising first, second and third segments (132a, 132b, 132c) extending downwardly and outwardly away from the process zone (122) or extending downwardly and inwardly into the process zone (122), in whole or in part, and a foot extension (134) extending upwardly or downwardly from an inner end to an outer end. Furthermore, the angles of the upward/downward/outward/inward inclination of the tube extension (132) comprising first, second and third segments (132a, 132b, 132c) and the foot extension (134) are provided as examples and are not limiting to implementations of the present disclosure. It should be noted that the thickness of the tube extension and/or foot extension (134) comprising the first, second, and third segments (132a, 132b, 132c) may vary across the length or width of the individual components and need not be uniform. Additionally, if a slope is present in any component of the sealing ring (132) (i.e., the tube extension (132) comprising the first, second, and third segments (132a, 132b, 132c) and/or the foot extension (134)), the slope need not be constant, but may vary along the direction of the individual components. It should also be appreciated that in some embodiments, the sealing ring (130) may be manufactured from separate pieces, for example, the tube extension (132) being separate from the foot extension (134). Additionally, the first, second, and third segments (132a, 132b, 132c) may be separate pieces. When the sealing ring (130) is manufactured as separate pieces, the pieces can be connected using mechanical fasteners, adhesives, screws, etc. In various sealing ring profiles, a foot extension (134) extending substantially above the top surface of the edge ring can mean that the foot extension (134) extends completely above the top surface of the edge ring (126). Alternatively, a foot extension (134) extending substantially above the top surface of the edge ring can mean that the foot extension (134) extends partially above the top surface of the edge ring (e.g., extends over an inner or outer portion of the edge ring).

In some implementations, the height (H1) of the tube extension (132) of the sealing ring (130) is defined to be about 20 mm to 65 mm. In another implementation, the height (H1) of the tube extension (132) is defined to be about 50 mm. In some implementations, the sealing ring (130) is constructed from aluminum. In some implementations, the sealing ring (130) is fabricated from anodized aluminum. In some implementations, the sealing ring (130) is coated with a material, such as Atomic Layer Deposition (ALD) Yttrium Oxide. In some implementations, the sealing ring is fabricated from a dielectric material, which would not require the use of a ground disconnect (140). In such embodiments, the dielectric material may include any one of Alumina, Yttria, Quartz, Silicon Nitride, Silicon Carbide, or combinations thereof. The list of genetic materials described above is provided merely as examples and should not be considered limiting.

In some implementations, the sealing ring (130) is integrated with the bottom showerhead (106b) to create a single-piece bottom showerhead having plasma sealing capabilities. It should be noted that the designs, dimensions, and materials used to define the other components of the process chamber (100) and the sealing ring (130) are provided as examples and should not be considered exhaustive or limiting.

FIG. 3 depicts a graph of etch rate as a function of distance from the center of a plotted wafer for an etching operation performed in a process chamber (100) using a sealing ring (130) having a foot extension (134). Based on testing and experimentation, the various graph lines plotted in the etch rate graph represent different etch profiles for different separations of the gap (136) (i.e., between the top surface of the edge ring (126) and the bottom surface of the foot extension (134) of the sealing ring (130), or between the top surface of the edge ring (126) and the bottom surface of the bottom showerhead). This graph demonstrates that different gaps can aid in tuning the etch performance to eliminate or reduce etch non-uniformity. Although the etch rate near the edge of the wafer will not always be exactly the same as the etch rate at the center of the wafer, these plots show significant improvement and increased etch rate uniformity near the wafer edge compared to prior art systems that do not use the sealing ring (130) with the foot extension (134) disclosed in the present invention.

For example, graph line 1 depicts a baseline etch rate profile extending from the center of the plotted wafer toward the wafer edge of a 300 mm wafer when no sealing ring is present. Graph lines 2-5 depict etch rate profiles when a sealing ring (130) with a foot extension is present and for different gaps defined between the foot extension (134) of the sealing ring (130) and the edge ring (126). Graph line 1 depicts an etch rate profile when the gap (136) between the top surface of the edge ring (126) and the bottom surface of the bottom showerhead is about 37.5 mm. Graph line 2 depicts an etch rate when the gap (136) between the top surface of the edge ring (126) and the foot extension (134) of the sealing ring (130) is about 17.7 mm. Graph line 3 represents the etching rate profile when the gap (136) between the top surface of the edge ring (126) and the foot extension (134) of the sealing ring (130) is about 12.7 mm.

Graph line 4 represents an etch rate profile when the gap (136) between the top surface of the edge ring (126) and the foot extension (134) of the sealing ring (130) is about 8.5 mm. Graph line 5 represents an etch rate profile similar to graph line (5) when the gap (136) between the top surface of the edge ring (126) and the foot extension (134) of the sealing ring (130) is about 6.5 mm. Based on the etch rate profiles of the various graph lines illustrated in the etch rate graphs of FIG. 3, to achieve a substantially uniform etch rate at the wafer edge, the gap (136) is defined to be, in some implementations, from about 3.5 mm to about 37.5 mm. In some other implementations, to achieve a substantially uniform etch rate at the wafer edge, the gap (136) is defined to be about 6 mm to about 20 mm. In yet other implementations, the gap (136) is defined to be about 13 mm. As illustrated, the sealing ring (130) having the foot extension (134) significantly assists in reducing the concentration gradient of radicals at the wafer edge, resulting in improved etch uniformity across the wafer up to and including the wafer edge.

The foregoing description of various implementations has been provided for the purpose of illustration and description. It is not intended to be exhaustive or limiting of the invention. Individual elements or features of a particular implementation are generally not limited to that particular implementation, but, where applicable, are interchangeable and may be used in a selected implementation, even if not specifically illustrated or described. The same may also be modified in many ways. Such modifications are not to be considered a departure from the invention, and all such modifications are intended to be included within the scope of the invention.

Although the foregoing embodiments have been described in some detail for purposes of clarity of understanding, it will be apparent that certain changes and modifications may be practiced within the scope of the appended claims. Accordingly, the present embodiments are to be considered illustrative and not restrictive, and the embodiments are not limited to the details provided herein, but may be modified within the scope of the claims and their equivalents.

Claims (21)

As a confinement ring for use in a process chamber,
A tubular extension configured to surround a process zone within the process chamber, the tubular extension having an upper end configured to be connected to a showerhead disposed within the process chamber and a lower end configured to extend proximate an edge ring, the edge ring configured to surround a wafer when the wafer is received within the process zone for processing; and
A foot extension comprising an inner end coupled to the lower end of the tube extension and extending outwardly from the process zone to the outer end, the foot extension defining an annular surface configured to form a gap with the uppermost surface of the edge ring, the gap being used to evacuate radicals from the process zone.
Sealing ring. In the first paragraph, the tube extension extends vertically downward from the showerhead at a right angle.
Sealing ring. In the first paragraph, the tube extension extends at an angle different from a right angle of the showerhead, and the angle is one of an acute angle and an obtuse angle with respect to the right angle.
Sealing ring. In the first paragraph, the annular surface of the foot extension is substantially parallel to the uppermost surface of the edge ring.
Sealing ring. In the fourth paragraph, the gap has a uniform height along the width of the foot extension.
Sealing ring. In the first paragraph, the foot extension extends substantially perpendicularly to the tube extension.
Sealing ring. In the first paragraph, the foot extension is extended at a taper angle different from a vertical angle with respect to the tube extension, and the taper angle is one of an acute angle and an obtuse angle.
Sealing ring. In the seventh paragraph, the gap has a height that varies along the width of the foot extension, and
The height of the above gap gradually increases or decreases outwardly,
Sealing ring. In the first paragraph, the width of the annular surface is the same as the width of the edge ring.
Sealing ring. In the first paragraph, the width of the annular surface is larger or smaller than the width of the edge ring.
Sealing ring. In the first paragraph, the size of the gap is defined to cause an increase in the velocity of radicals flowing through the gap and prevent backflow of radicals.
Sealing ring. In the first paragraph, the showerhead includes a top showerhead and a bottom showerhead, and the tube extension is connected to the bottom showerhead.
Sealing ring. In the first paragraph, the sealing ring is integrated into the showerhead,
Sealing ring. In the first aspect, the wafer is received on an upper surface of an electrostatic chuck (ESC) defined in a lower portion of the process chamber, and the inner diameter of the sealing ring extends to an outer diameter of the wafer received on the upper surface of the ESC, such that the tube extension is aligned with an outer edge of the wafer and an annular surface of the foot extension extends substantially above the upper surface of the edge ring.
Sealing ring. In the first aspect, the uppermost surface of the sealing ring includes a groove for receiving an O-ring, the O-ring being used to create a seal when the sealing ring is connected to the showerhead.
Sealing ring. In the first aspect, the sealing ring is manufactured from one of aluminum, anodized aluminum, and aluminum coated with ALD (Atomic Layer Deposition) Yttria or a dielectric material.
Sealing ring. As a process chamber used for etching wafers,
A lower portion of the process chamber, an electrostatic chuck (ESC) configured to receive the wafer, the ESC defined by a top surface and an edge ring, the edge ring being positioned adjacent the wafer and configured to surround the wafer;
A plasma chamber defined in an upper portion of the process chamber, wherein the plasma chamber comprises one or more coils coupled to one or more gas sources for receiving process gas(es) and arranged to surround the plasma chamber, the one or more coils being coupled to an RF power source via a matching network for receiving RF power, the RF power being used to heat the process gas(es) to generate a plasma;
A showerhead defined on the floor of the plasma chamber, the showerhead having an inlet for directing radicals of the plasma toward a process zone defined between the showerhead and the ESC of the process chamber;
A sealing ring for use in the above process chamber, the sealing ring comprising:
a tube extension configured to surround the process region within the process chamber, the tube extension having an upper end configured to connect to a bottom surface of the showerhead disposed within the process chamber and a lower end configured to extend proximate the edge ring surrounding the wafer; and
A foot extension having an inner end coupled to a lower end of the tube extension and extending outwardly from the process zone to the outer end, the foot extension defining an annular surface configured to form a gap with an uppermost surface of the edge ring, the gap being used to direct plasma away from the process zone.
Process chamber. In the 17th paragraph, the showerhead includes a top showerhead and a bottom showerhead, and the tube extension of the sealing ring is connected to the bottom showerhead.
Process chamber. In the 17th paragraph, the inner diameter of the sealing ring extends to the outer diameter of the wafer received on the uppermost surface of the ESC, and the tube extension is aligned with the outer edge of the wafer when the wafer is received on the ESC.
Process chamber. In the 17th paragraph, the tube extension extends vertically downward from the showerhead at a right angle, and
The annular surface of the foot extension is substantially parallel to the uppermost surface of the edge ring;
Process chamber. As a sealing ring for use in a process chamber,
A tube extension configured to surround a process zone within said process chamber, said tube extension having an upper end configured to be connected to a top plate of said process chamber and a lower end configured to extend proximate an edge ring, said edge ring configured to surround a wafer when the wafer is received within said process zone for processing; and
A foot extension having an inner end coupled to a lower end of the tube extension and extending outwardly from the process zone to an outer end, the foot extension defining an annular surface configured to form a gap with an uppermost surface of the edge ring, the gap being used to direct plasma away from the process zone.
Sealing ring.